Laser drilled holes for film cooling

Abstract

A hole geometry and laser drilling technique for forming a shaped diffusing film coolant passage having a straight constant cross section metering portion which connects with a conical section which exits on the surface to be cooled. The metering portion of the hole provides for air quantity metering while the tapered portion provides a diffusion effect on the cooling air so that upon exit the cooling air remains attached to the surface to be cooled and thereby provide effective film cooling.

What is claimed is:  
     
       1. A gas turbine engine component which includes at least one laser drilled hole having a conical portion with an apex, with an included apex angle of 8-20° and a constant cross section metering portion which intersects said cone in the region of said cone apex. 
     
     
       2. A gas turbine engine component as in  claim 1  wherein said laser drilled hole has an apex angle of about 10° to about 16°. 
     
     
       3. A gas turbine engine component as in  claim 1  wherein said hole has a metering portion with a cross sectional area equivalent to that of a circular hole having a diameter of about 0.010 in. to about 0.040 in. 
     
     
       4. A gas turbine engine component as in  claim 1  wherein said conical portion of said hole and said metering portion of said hole are essentially coaxial. 
     
     
       5. A gas turbine engine component as in  claim 1  wherein the metering section of said hole changes its diameter by from 0.001 to 0.005 in. over its length.